Phase-locked loops (PLL) find widespread use in frequency synthesizers, clock recovery circuits, phase modulators, and frequency demodulators. Generally, a PLL consists of a voltage-controlled oscillator (VCO), counter, phase/frequency detector (P/FD), charge pump (CP), and low pass filter as shown in FIG. 1. The PLL uses feedback to track the phase of the input signal and generate a replica signal, usually offset in frequency.
The behavior of a phase-locked loop system depends on the parameters associated with each of the comprising circuits. These parameters vary with process and affect the system's performance—even its stability. It would therefore be advantageous to have a system to precisely set the phase-locked loop's operating parameters.